This invention relates to a control valve with valve element which is mounted in a valve body and bears in the closed position on a valve seat, to block a fluid passage formed in the valve body, and can be moved into an open position by axial movement of an actuating rod.
Such a control valve is known from FR-A 1 378 578 for example. The control valve employed there serves in particular for turning spray systems on and off. The closed position is attained by actuating a hand lever, which acts on an actuating rod (plunger), at the front end of which is arranged a conical valve element. The valve element is biased on to the valve seat by at least one compression spring, to block the fluid passage. In order to achieve a high closing force of the valve in this closed position, relatively strong compression springs are usually employed, which however require relatively high actuating forces for switching the control valve into the open or free-passage position. Accordingly a multi-part actuating lever is proposed in the cited reference, with an appropriate mechanical advantage, but the construction is very expensive. In addition this normal construction with a plurality of transmission levers is prone to wear, especially with frequent switching operations. Moreover the structural volume of such a control valve is increased in a disadvantageous manner.
In consequence the invention is based on the object of avoiding the above disadvantages and providing a control valve which has a high closing force with a small actuating force, as well as facilitating a simple and compact construction.
One aspect of the invention involves a control valve having a valve body and a valve seat mounted within the valve body. A valve element is mounted in the valve body and bears in a closed position on the valve seat to block a fluid passage formed in the valve body. An actuating rod is configured for axial movement and acts upon the valve element to move the valve element into an open position. At least one of the actuating rod and the valve element has an annular piston surface and is in communication with a fluid passage through an equalizing line.
The formation of an annular piston surface on the actuating rod and of an equalizing line, which is in communication with the fluid passage, leads to the result that pressure occurring in the fluid line is passed to the rear side of the valve element and there increases the closing force of the valve element by acting on the annular piston surface. A xe2x80x9cbalancing outxe2x80x9d matched to the currently applied pressure is thus obtained. It should be noted that the annular piston surface has a larger effective piston area than in comparison with area of the sealing surface of the valve element, so that the valve element is always biased in the direction of the closed position.
This makes it possible in preferred manner to use a relatively weak compressing spring, since the required closing force is achieved in particular by the action of the fluid on the annular piston surface. Accordingly even a relatively short hand lever can be used to operate the control valve, or a correspondingly compact spindle or eccentric drive or pneumatic cylinder. A particularly compact overall construction results from this.
In an advantageous embodiment the piston area is formed in one piece with the actuating rod for the valve element, namely as a simple turned part, on which an annular shoulder is formed as the piston surface. In addition this annular piston surface can be formed as an abutment surface for the compression spring.
In a particularly simple construction the equalizing line is passed centrally through the actuating rod, for example in the form of a central bore and a transverse channel bore joining this. A particularly simple manufacture results from this. However the equalizing line can also be formed outside, in the valve body or eccentrically in the actuating rod, especially if a central fluid passage is desired.